One of the visits we had planned was to the UN Headquarters, on 1st Avenue and 46th Street. The UN is in an area declared international territory, so for a few hours we were outside the United States. It has its own postage stamps and its own post office, so one of the favorite activities for visitors is sending themselves a postcard with stamp and postmark from the UN.
They have guided tours, and if you call in advance they will tell you the schedule of tours in different languages. In the tour they take you through several panels and expositions about the UN, its creation and its mission, and they show you the meeting halls. We couldn't see the Security Council because it was in session, but we saw the General Assembly, which we all have seen many times on TV.
